Japan’s 12,000-tonne Aegis ships promise stronger missile defense – but could concentrate the threat in ways that echo past naval failures.
Last month, Naval News reported that Japan’s Ministry of Defense confirmed that the construction of two Aegis-equipped vessels (ASEV) had entered the main production phase following the successful deployment of both hulls at major domestic shipyards.
The program, which emerged as a sea-based alternative to the canceled Aegis Ashore system, represents a significant investment in Japan’s ballistic missile defense architecture.
This concentration of capability on a small number of high-value platforms echoes a recurring dilemma in naval warfare: whether more power on fewer troops increases deterrence—or causes catastrophic losses.
The first hull was launched at the Mitsubishi Heavy Industries shipyard in Nagasaki in July 2025, while the second followed at Japan Marine United’s Isogo facility in February 2026. These milestones mark a shift towards continuous sea-based missile defense coverage of the Japanese archipelago.
Scheduled to be commissioned in 2028 and 2029, the 12,000-tonne vessels – roughly 190 meters in length – are expected to be classified as guided-missile (CG) cruisers due to their size.
Each ship will be equipped with 128 vertical launch cells, surpassing the 96 cells on Japan’s latest Aegis destroyers, and will deploy SM-3 Block IIA and SM-6 interceptors, along with Tomahawk cruise missiles in support of Japan’s counter-attack capability.
At the heart of the design is the AN/SPY-7 radar, intended to provide long-range surveillance and tracking of ballistic missile threats. The ships are designed to carry out continuous missile monitoring missions, providing coverage of the Japanese archipelago. They will also relieve existing Aegis destroyers of ongoing ballistic missile defense duties, allowing them to return to broader multi-mission operations.
The scale of the regional missile inventory underscores the rationale for this approach. According to the US Department of Defense (DoD) China Military Power Report 2025 (CMPR)China possesses about 500 intermediate-range ballistic missiles (IRBMs) with a range of up to 5,000 kilometers, 1,300 medium-range ballistic missiles (MRBMs) and 400 land-launched cruise missiles, many of which have a range sufficient to hit targets in Japan.
This threat is compounded by North Korea’s increasingly sophisticated missile program, which threatens the missiles endnoteS emphasizes asymmetric deterrence through IRBM and MRBM platforms such as Nodong-1 and Hwasong-12. The report further states that North Korea is improving tactics such as salvo launches and multi-azimuth attacks specifically designed to defeat traditional BMD systems.
These developments, combined with the establishment of hypersonic the weapons AND drone batcheshave created a threat environment where Japan’s Defense White Paper 2025 admits it is becoming increasingly difficult to respond effectively with the current two-tier network of eight Aegis destroyers and Patriot batteries.
Dimitris Mitsopoulos and Kosuke Takahashi debate in a March 2025 Maritime News ITEM that the ASEV’s greater displacement and enhanced launch capacity increases its ability to support missile defense operations, while the transition from the SPY-1 to the SPY-7 radar provides significantly greater tracking capability, including the ability to handle multiple simultaneous ballistic missile threats.
However, Sidharth Kaushal, writing in a March 2023 European Security and Defence ITEMargues that large warships remain vulnerable due to the proliferation of advanced anti-ship weapons.
He notes that modern missiles, especially hypersonic systems that combine speed and maneuverability, can strain a ship’s air and missile defenses, while the cost asymmetry favors the attacker, who can absorb more failures than defenders can tolerate successful hits.
These weaknesses extend beyond high-end rockets to low-cost consumables. Small, low-flying drones can “mission kill” a ship like an ASEV by targeting exposed systems such as radar arrays, communications nodes and engine inlets. Optimized for tracking high-velocity ballistic threats, the ship’s sensors can struggle to detect slow, low-signature targets, allowing drones to approach undetected.
Even limited damage to these critical components can disable combat functions without sinking the ship, forcing lengthy repairs and taking it out of combat. In this sense, survival is not simply a function of protective systems, but how much danger is concentrated in a single hull.
At the same time, the ASEV’s larger size can provide the space, weight and power limits needed to accommodate future systems such as rail weapons, which Japan has already tested at sea.
Unlike traditional weapons, railguns use electromagnetic force to propel projectiles at hypersonic speeds, potentially providing a lower-cost means of countering missile creeps and drone swarms if the technology matures. But such possible adaptations do not solve the fundamental issue of concentrating critical capabilities on a small number of high-value platforms.
Kaushal points out that large warships are neither obsolete nor invulnerable and that their survival depends on fleet size, coordination and the ability to absorb losses in contested environments. This raises concerns that Japan may be preparing for a future naval conflict with past approaches to sea power.
This necessity for a more flexible fleet architecture may be why Ridzwan Rahmat notes in a June 2023 Janes REPORT that the ASEVs will allow Japan to return its existing Aegis destroyers to fleet air defense roles, supporting Japan’s growing return to carrier-based aviation. The shift is most noticeable in the conversion of Helicopter carriers JS Izumo and JS Kaga to operate F-35B fightersa project expected to be completed this year.
Brendon Cannon and Ash Rossiter score in an October 2021 ITEM in the Asian Security Journal that these carriers will function as mobile air bases, providing essential air cover to remote territories such as the Senkaku Islands, where land-based airfields are either absent or highly targeted.
However, Olli Suorsa and John Bradford debate their October 2021 Fight on the Rocks ITEM that the strategic value of these carriers remains debatable. Suorsa and Bradford point out that, with a capacity for only about a dozen aircraft, these ships lack the ability to generate flights of full-sized carriers and lack critical capabilities such as airborne organic early warning and refueling.
They suggest that land-based distributed airpower can provide a more resilient and cost-effective solution to the anti-access/area denial (A2/AD) threat posed by China.
Ultimately, the ASEV program and the broader restructuring of Japan’s forces represent a big bet on concentrating capability on a small number of large platforms. While specialization can improve performance, it also creates profitable targets in the era of precision strike and mass attack.
The parallel with the battleship Yamato is not just historical symbolism, but strategic logic: when too much combat power is concentrated in too few troops, survival becomes a matter not of power but of exposure.
